Catheter for delivery of energy to a surgical site

ABSTRACT

A catheter for delivering energy to a surgical site is disclosed. The catheter includes at a proximal end a handle and at a distal end a probe. The catheter includes at least one energy delivery device and an activation element. The activation element is located at the distal end of the catheter, to transition the probe from a linear to a multi-dimensional shape, within the surgical site. In another embodiment of the invention the catheter includes an energy delivery element, a tip and a blade. The energy delivery element is located at the distal end of the catheter to deliver energy to portions of the intervertebral disc. The blade is positioned within a first lumen of the tip and is extensible beyond the tip, to cut selected portions within the intervertebral disc. In another embodiment of the invention a catheter includes both energy and material transfer elements and an interface on the handle thereof. The interface couples the energy delivery element and the material transfer element to external devices for energy and material transfer to and from the intervertebral disc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/898,671, filed Jul. 26, 2004, which is a continuation of U.S. patentapplication Ser. No. 09/776,231, filed Feb. 1, 2001, now U.S. Pat. No.6,676,347, which is a divisional of U.S. patent application Ser. No.09/272,806, filed Mar. 19, 1999, now U.S. Pat. No. 6,258,086, whichclaims priority to provisional application Ser. No. 60/078,545 filed onMar. 19, 1998. U.S. patent application Ser. No. 09/272,806 is also acontinuation-in-part of U.S. patent application Ser. Nos. 08/881,527,now U.S. Pat. No. 5,980,504, 08/881,525, now U.S. Pat. No 6,122,549,08/881,692, now U.S. Pat. No. 6,073,051, 08/881,693, now U.S. Pat. No.6,007,570, and 08/881,694, now U.S. Pat. No. 6,095,149, each of whichwere filed on Jun. 24, 1997, and each of which claims priority to U.S.Provisional Application Nos. 60/047,820, 60/047,818, and 60/047,848,each of which were filed on May 28, 1997, U.S. Provisional ApplicationNo. 60/047,941, filed May 8, 1997, and U.S. Provisional Application Nos.60/029,734, 60/029,735, 60/029,600, and 60/029,602, each of which werefiled on Oct. 23, 1996. Application Ser. Nos. 10/898,671, 09/776,231,09/272806, 08/881,525, 08/881,692, 08/881,693, 08/881,694, 60/047,941,60/078,545, and 60/029,734 are each hereby incorporated by reference asif fully set forth herein.

BACKGROUND

1. Field of the Invention

This invention relates to methods and apparatuses to treatintervertebral disc problems and/or for modifying intervertebral disctissue. More particularly this invention relates to percutaneoustechniques to avoid major surgical intervention. In one embodiment,annular fissures are treated by radio frequency (RF) heating ofintervertebral disc issue.

2. Description of Related Art

Intervertebral disc abnormalities (e.g., morphologic) have a highincidence in the population and may result in pain and discomfort ifthey impinge on or irritate nerves. Disc abnormalities may be the resultof trauma, repetitive use, metabolic disorders and the aging process andinclude such disorders but are not limited to degenerative discs (i)localized tears or fissures in the annulus fibrosus, (ii) localized discherniations with contained or escaped extrusions, and (iii) chronic,circumferential bulging disc.

Disc fissures occur rather easily after structural degeneration (a partof the aging process that may be accelerated by trauma) of fibrouscomponents of the annulus fibrosus. Sneezing, bending or just attritioncan tear these degenerated annulus fibers, creating a fissure. Thefissure may or may not be accompanied by extrusion nucleus pulposusmaterial into or beyond the annulus fibrosus. The fissure itself may bethe sole morphological change, above and beyond generalized degenrativechanges in the connective tissue of the disc. Even if there is novisible extrusion, biochemicals within the disc may still irritatesurrounding structures. Disc fissures can be debilitatingly painful.Initial treatment is symptomatic, including bed rest, pain killers andmuscle relaxants. More recently spinal fusion with cages has beenperformed when conservative treatment did not relieve the pain. Thefissure may also be associated with a herniation of that portion of theannulus.

With a contained disc herniation, there are no free nucleus fragments inthe spinal canal. Nevertheless, even a contained disc herniation isproblematic because the outward protrusion can press on the spinalnerves or irritate other structures. In addition to nerve rootcompression, escaped nucleus pulposus contents may chemically irritateneural structures. Current treatment methods include reduction ofpressure on the annulus by removing some of the interior nucleuspulposus material by percutaneous nuclectomy. However, complicationsinclude disc space infection, nerve root injury, hematoma formation,instability of the adjacent vertebrae and collapse of the disc fromdecrease in height.

Another disc problem occurs when the disc bulges outwardcircumferentially in all directions and not just in one location. Overtime, the disc weakens and takes on a “roll” shane or circumferentialbulge. Mechanical stiffness of the joint is reduced and the joint maybecome unstable. One vertebra may settle on top of another. This problemcontinues as the body ages, and accounts for shortened stature in oldage. With the increasing life expectancy of the population, suchdegenerative disc disease and impairment of nerve function are becomingmajor public health problems. As the disc “roll” extends beyond thenormal circumference, the disc height may be compromised, and foraminawith nerve roots are compressed. In addition, osteophytes may form onthe outer surface of the disc roll and further encroach on the spinalcanal and foramina through which nerves pass. This condition is calledlumbar spondylosis.

It has been thought that such disc degeneration creates segmentalinstability which disturbs sensitive structures which in turn registerpain. Traditional, conservative methods of treatment include bed rest,pain medication, physical therapy or steroid injection. Upon failure ofconservative therapy, spinal pain (assumed to be due to instability) hasbeen treated by spinal fusion, with or without instrumentation, whichcauses the vertebrae above and below the disc to grow solidly togetherand form a single, solid piece of bone. The procedure is carried outwith or without discectomy. Other treatments include discectomy alone ordisc decompression with or without fusion.

Nuclectomy can be performed by removing some of the nucleus to reducepressure on the annulus. However, complications include disc spaceinfection, nerve root injury, hematoma formation, and instability ofadjacent vertebrae.

These interventions have been problematic in that alleviation of backpain is unpredictable even if surgery appears successful. In attempts toovercome these difficulties, new dixation devices have been introducedto the market, including but not limited to pedicle screws and interbodyfusion cages. Although pedicle screws provide a high fusion successrate, there is still no direct correlation between fusion success andpatient improvement in function and pain. Studies on fusion havedemonstrated success rates of between 50% and 67% for pain improvement,and a significant number of patients have more pain postoperatively.Therefore, different methods of helping patients with degenerative discproblems need to be explored.

FIGS. 1A and 1B illustrate a cross-sectional anatomical view of avertebra and associated disc and a lateral view of a portion of a lumbarand thoracic spine, respectively. Structures of a typical cervicalvertebra (superior aspect) are shown in FIG. 1A: 104—lamina; 106—spinalcord; 108—dorsal root of spinal nerve; 114—ventral root of spinal nerve;116—posterior longitudinal ligament; 118—intervertebral disc;120—nucleus pulposus; 122—annulus fibrosus; 124—anterior longitudinalligament; 126—vertebral body; 128—pedicle; 130—vertebral artery;132—vertebral veins; 134—superior articular facet; 136—posterior lateralportion of the annulus; 138—posterior medial portion of the annulus; and142—spinous process. In FIG. 1A, one side of the intervertebral disc 118is not shown so that the anterior vertebral body 126 can be seen. FIG.1B is a lateral aspect of the lower portion of a typical spinal columnshowing the entire lumbar region and part of the thoracic region anddisplaying the following structures: 118—intervertebral disc;126—vertebral body; 142—spinous process; 170—inferior vertebral notch;172—spinal nerve; 174—superior articular process; 176—lumbar curvature;and 180—sacrum.

The presence of the spinal cord (nerve sac) and the posterior portion ofthe vertebral body 126, including the spinous process 142, and superiorand inferior articular processes 110, prohibit introduction of a needleor trocar from a directly posterior position. This is important becausethe posterior disc wall is the site of symptomatic annulus tears anddisc syndromes. The inferior articular process, along with the pedicle128 the lumbar spinal nerve, form a small “triangular” window 168 (shownin black in FIG. 1C) through which introduction can be achieved from theposterior lateral approach. FIG. 1D looks down on an instrumentintroduced by the posterior lateral approach. It is well known to thoseskilled in the art that percutaneous access to the disc is achieved byplacing an introducer into the disc from this posterior lateralapproach, but the triangular window does not allow much room tomaneuver. Once the introducer pierces the tough annulus fibrosus, theintroducer is fixed at two points along its length and has very littlefreedom of movement. Thus, this approach has allowed access only tosmall central and anterior portions of the nucleus pulposus. Currentmethods do not permit percutaneous access to the posterior half of thenucleus or to the posterior wall of the disc. Major and potentiallydangerous surgery is required to access these areas.

U.S. Pat. No. 5,433,739 (the “'739 patent”) discloses placement of an RFelectrode in an interior region of the disc approximately at the centerof the disc. RF power is applied , and heat then putatively spreads outglobally throughout the disc. The '739 patent teaches the use of a rigidshaft which includes a sharpened distal end that penetrates through theannulus fibrosus and into the nucleus pulposus. In one embodiment theshaft has to be rigid enough to permit the distal end of the RFelectrode to pierce the annulus fibrosus, and the ability to maneuverits distal end within the nucleus pulposus is limited. In anotherembodiment, a somewhat more flexible shaft is disclosed. However,neither embodiment of the devices of the '739 patent permits access tothe posterior, posterior lateral and posterior medial region of thedisc, nor do they provide for focal delivery of therapy to a selectedlocal region within the disc or precise temperature control at theannulus. The '739 patent teaches the relief of pain by globally heatingthe disc. There is no disclosure of treating an annular tear or fissue.

U.S. Pat. No. 5,201,729 (the “'729 patent”) discloses the use of anoptical fiber that is introduced into a nucleus pulposus. In the '729patent, the distal end of a stiff optical fiber shaft extends in alateral direction relative to a longitudinal axis of an introducer. Thisprevents delivery of coherent energy into the nucleus pulposus in thedirection of the longitudinal axis of the introducer. Due to theconstrained access from the posterior lateral approach, stiff shaft andlateral energy delivery, the device of the '729 patent is unable to gainclose proximity to selected portion(s) of the annulus (i.e., posterior,posterior medial and central posterior) requiring treatment or toprecisely control the temperature at the annulus. No use in treating anannular fissure is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear conception of the advantages and features constituting thepresent invention, and of the components and operation of model systemsprovided with the present invention, will become more readily apparentby referring to the exemplary, and therefore nonlimiting, embodimentsillustrated in the drawings accompanying and forming a part of thisspecification, wherein like reference numerals (if they occur in morethan one view) designate the same elements. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.

FIG. 1A is a superior cross-sectional anatomical view of a cervical discand vertebra.

FIG. 1B is a lateral anatomical view of a portion of a lumbar spine.

FIG. 1C is a posterior-lateral anatomical view of two lumbar vertebraeand an illustration of the triangular working zone, representing anembodiment of the present invention.

FIG. 1D is a superior cross-sectional view of the required posteriorFIG. 2A is a plan view of an introducer and an instrument of theinvention in which solid lines illustrate the position of the instrumentin the absence of bending forces and dotted lines indicate the positionthe distal portion of the instrument would assume under bending forcesapplied to the intradiscal section of the instrument, representing anembodiment of the present invention.

FIG. 2B is an end view of the handle of the embodiment shown in FIG. 2A.

FIG. 3 is a side view of a catheter with a elastically deformed endsection with an arcuate shape.

FIGS. 4A-D show the surgical steps connected with the insertion of thecatheter of FIG. 3 into a surgical site.

FIG. 5 is a side view of a catheter with a elastically deformed endsection with an inward spiral shape.

FIG. 6A-6B is a side view of a catheter with a elastically deformed endsection with an outward spiral shape.

FIG. 7 is a side view of a catheter with a clastically deformed endsection with an “eggbeater” shape.

FIGS. 8A-F are isometric views of an alternate embodiment of theinvention in which the probe of the catheter performs an electrophoreticfunction.

FIGS. 9A-D show the surgical steps connected with the insertion of thecatheter of FIGS. 7-8 into a surgical site.

FIGS. 10A-B show catheters with thermal energy delivery sources.

FIG. 11 shows a thermal delivery element for a catheter.

FIGS. 12A-C show a catheter probe with a knife, lumen, and energyelement.

FIG. 13 shows a catheter connector including fluid delivery coupling.

FIG. 14 shows another connector with fluid delivery coupling.

SUMMARY OF THE INVENTION

Accordingly, it is desirable to diagnose and treat disc abnormalitiessuch as disc degeneration at locations previously not accessible viapercutaneous approaches and without major surgical intervention orsubstantial destruction to the disc. It would be further desirable totreat disc abnormalities via controlled high-energy input availablethrough radio frequency energy. It would be further desirable to providesuch RF energy to the nucleus pulposus at the posterior, posteriorlateral and the posterior medial regions of the inner wall of theannulus fibrosis, without heating other regions of the nucleus, as wouldoccur with prior art heating elements. It would further be desirable tobe able to administer materials to, or remove materials from, a precise,selected location within the disc, particularly to the location of theannular fissure. It would be further desirable to provide thermal energyinto collagen in the area of the fissure to strengthen the annulus andpossibly fuse collagen to the sides of the fissure, particularly at theposterior, posterior lateral and the posterior medial regions of theinner wall of the annulus fibrosus.

A primary object of the invention is to provide a minimally invasivemethod and apparatus for diagnosing and treating fissures of discs atselected locations within the disc.

Another object of the invention is to provide a minimally invasivemethod and apparatus for treating morphological abnormalities of discsat selected locations within the disc via radio frequency electrodes.

Another object of the invention is to provide a device which has adistal end that is inserted into the disc and accesses the posterior,posterior lateral and the posterior medial regions of the inner wall ofthe annulus fibrosis for application of RF energy at such location.

Another object of the invention is to provide an apparatus which idadvanceable and naviagable at the inner wall of the annulus fibrosus toprovide localized heating at the site of the annular fissure.

Another object of the invention include providing apparatus and methodsfor diagnosing an abnormality and/or adding or removing a material at apreselected location of a disc via a function element.

Another object of the invention is to provide a device which has adistal end that is inserted into the disc and accesses the posterior,posterior lateral and the posterior medial regions of the inner wall ofthe annulus fibrosus in order to repair or shrink an annular fissure atsuch a location.

Another object of the invention is to provide a non-destructive methodand apparatus for treating morphologic abnormalities of discs.

Another object of the invention is to provide a method and apparatus totreat degenerative intervertebral discs by delivering thermal energy todenervate selective nerves embeeded in the walls of the disc.

Another objective of the invention is to provide a method and apparatusto treat degenerative intervertebral discs by delivering thermal energyto cauterize granulation tissue that is ingrown in the wall of the disc.

Another object of the invention is to provide a method and apparatus totreat degenerative intervertebral discs by delivering thermal energy tobreak down selected enzyme systems and neurotransmitters that generatepain within the disc.

Another object of the invention is to provide a method and apparatus totreat degenerative intervertebral discs by shrinking a selected amountof collagen in the annulus fibrosis of the disc and remove a redundancyin the disc roll.

Another object of the invention is to provide a method and apparatus totreat degenerative intervertebral discs by delivering thermal energy toat least a portion of the nucleus pulposus to reduce water content ofthe nucleus pulposus and shrink the nucleus pulposus without creating acontained herniated disc.

Another object of the invention is to provide a method and apparatus totreat degenerative intervertebral discs by supplying sufficient thermalenergy to shrink the nucleus pulposus and tighten the disc.

Another object of the invention is to provide an apparatus to treatdegenerative intervertebral discs which is advanceable and navigationaladjacent to an inner wall of the annulus fibrosis.

Another object of the invention is to provide a thermal energy deliverydevice which has a distal end that is inserted into the nucleus pulposusand accesses the posterior, posterior lateral and the posterior centralregions of the inner wall of the nucleus fibrosis.

The invention provides an intervertebral disc apparatus that includes anintroducer with an introducer lumen and a catheter. The catheter is atleast partially positioned in the introducer lumen and includes a probesection and an energy delivery device coupled to the intradiscalsection. The intradiscal section is configured to be advanceable througha nucleus pulposus of the intervertebral disc and positionable adjacentto a selected site of an inner wall of an annulus fibrosis. The energydelivery device is configured to deliver sufficient energy to heat atleast a portion of the intervertebral disc without substantiallyremoving intervertebral disc material positioned adjacent to the energydelivery device.

The invention also includes providing an externally guidableintervertebral disc apparatus for manipulation of disc tissue present ata preselected location of an intervertebral disc, the disc having anucleus pulposus, an annulus fibrosis, and an inner wall of the annulusfibrosis, the nucleus pulposus having a first diameter and a discplaying between opposing sections of the inner wall, proximity to thenucleus being provided by an introducer comprising an internalintroducer lumen with an opening at a terminus of the introducer,comprising a catheter having a distal end and a proximal end having alongitudinal access, the catheter being adapted to slidably advancethrough the introducer lumen, the catheter having an intradiscal sectionat the distal end of the catheter, the intradiscal section beingextendable through the opening of the introducer and having sufficientrigidity to be advanceable through the nucleus pulposus of the disc andaround the inner wall of the annulus fibrosis under a force appliedlongitudinally to the proximal end and having insufficient penetrationability to be advanceable through the inner wall of the annulus fibrosisunder the force; and a heating element located at the intradiscalsection selected from the group consisting of RF heating elements,resistive heating elements, chemical heating elements, and ultrasoundheating elements.

An embodiment of the invention is based on a catheter for deliveringenergy to a surgical site. The catheter includes at a proximal end ahandle and at a distal end a probe. The catheter includes at least oneenergy delivery device and an activation element. The at least oneenergy delivery device is located at the distal end of the catheter todeliver energy to portions of the surgical site. The activation elementis located at the distal end of the catheter, to transiton the probefrom a linear to a multi-dimensional shape, within the surgical site. Inanother embodiment of the invention the catheter includes a substrateand a heating element. The substrate is located at the distal end of thecatheter. The heating element is fabricated on the substrate byphoto-etching to deliver thermal energy to portions of the surgicalsite.

In another embodiment of the invention the catheter includes a firstprobe section, at least one energy delivery element, a tip and a blade.The first probe section defines along a length thereof a first lumen.The at least one energy delivery element is located at the distal end ofthe catheter to deliver energy to portions of the intervertebral disc.The tip is coupled to the first probe section at a terminus thereof. Thetip defines on an exterior face a second lumen substantially concentricwith said first lumen. The blade is positioned within the first lumenand is extensible from a first position within said first probe section,to a second position extending through the second lumen and beyond thetip, to cut selected portions within the intervertebral disc.

In another embodiment of the invention a catheter includes an energydelivery element, a material transfer element, and at least oneinterface on the handle thereof. The energy delivery element is locatedat the distal end of the catheter to deliver energy to portions of theintervertebral disc. The material transfer element is located at thedistal end of the catheter to transfer material to and from theintervertebral disc. The at least one interface on the handle couplesthe energy delivery element and the material transfer element toexternal devices for energy and material transfer to and from theintervertebral disc.

In still another embodiment of the invention a method for deploying aprobe portion of a catheter in a multi-dimensional shape within asurgical site is disclosed. The method includes the steps of:configuring the probe of the catheter in a substantially linearconfiguration; applying a sufficient force to advance the probe of thecatheter through the nucleus pulposus, which force is insufficient topuncture the annulus fibrosus; deploying the probe in a substantiallyarcuate configuration within the inner wall of the annulus fibrosus, anddelivering energy from the probe to portions of the intervertebral disc.

In another embodiment of the invention a catheter for treating anintervertebral disc is disclosed. The catheter includes anelectrophoretic element located at the distal end of the catheter toalter the milieu within the intervertebral disc.

DETAILED DESCRIPTION

The present invention provides a method and apparatus for treatingintervertebral disc disorders by the application of controlled heatingto a localized-region of an intervertebral disc. Such disorders includebut are not limited to (i) degenerative discs which have tears orfissures in the annulus fibrosis, particularly fissures of the annulusfibrosis, which may or may not be accompanied with contained or escapedextrusions, (ii) contained disc herniations with focal protrusions, and(iii) bulging discs.

Degenerative discs with tears or fissures are treated non-destructivelywithout the removal of disc tissue other than limited ablation to thenucleus pulposus which changes some of the water content of the nucleuspulposus. Nothing is added to supplement the mechanics of the disc.Electromagnetic energy is delivered to a selected section of the disc inan amount which does not create a destructive lesion to the disc, otherthan at most a change in the water content of the nucleus pulposus. Inone embodiment, there is no removal and/or vaporization of disc materialpositioned adjacent to an energy delivery device positioned in a nucleuspulposus. Sufficient electromechanical energy is delivered to the discto change its biochemical, neurophysiologic and/or biomechanicalproperties. Neurophysiologic modifications include denervation ofnociceptores in a tear or fissure in the annulus fibrosis.

Degenerative intervertebral discs with fissures are treated bydenervating selected nerves that are embedded in the interior was of theannulus fibrosis as well as nerves outside of the interior wallincluding those on the surface of the wall. Electromagnetic energy isused to cauterize granulation tissue which are pain sensitive areas andformed in the annulus fibrosis wall. Electromagnetic energy is also usedto break down selected enzyme systems and neurotransmitters thatgenerate pain within the disc. Generally, these enzymes andneurotransmitters only work within a small bandwidth of both pH andtemperature.

Electomagnetic energy is applied to shrink collagen in the annulusfibrosis and/or nucleus pulposus. This reduces the redundancy in thedisc roll that is created in a degenerative disc. Deliver ofelectromagnetic energy to the nucleus pulposus removes some water andpermits the nucleus pulposus to withdraw. This reduces a “pushing out”effect that created a contained herniation. Combinations of shrinkingthe disc, shrinking of the nucleus pulposus by reducing water content,as well as tightening up the annulus fibrosis wall creates arejuvenation of the disc. Reducing the pressure in the disc andtightening the annulus fibrosis produces a favorable biomechanicaleffect. Application of electromagnetic energy locally increases thestiffness of the disc.

the annulus fibrosis is comprised primarily of fibrosis-like materialand the nucleus pulposus is comprised primarily of an amorphouscolloidal gel. The distinction between the annulus fibrosis and thenucleus pulposus becomes more difficult to distinguish when a patient is30 years old or greater. There is often a transition zone between theannulus fibrosis and the nucleus pulposus made of fibrosis-like materialand amorphous colloidal gel. For purposes of this disclosure, the innerwall of the annulus fibrosis includes the young wall comprised primarilyof fibrosis-like material as well as the transition zone which includesboth fibrous-like material and amorphous colloidal gels (hereinaftercollectively referred to as “inner wall of the annulus fibrosis”).

In general, an apparatus of the invention is in the form of anexternally guidable intervertebral disc apparatus for accessing andmanipulating disc tissue present at a selected location of anintervertebral disc having a nucleus pulposus and an annulus fibrosus,the annulus having an inner wall. Use of a temperature-controlled energydelivery element, combined with the navigational control of theinventive catheter, provides preferential, localized heating to treatthe fissure. For ease of reference to various manipulations anddistances described below, the nucleus pulposus can be considered ashaving a given diameter in a disc plane between opposing sections of theinner wall. This nucleus pulposus diameter measurement allows instrumentsizes (and parts of instruments) designed for one size disc to bereadily converted to sizes suitable for an instrument designed for adifferent size of disc.

The operational portion of the apparatus of the invention is brought toa location in or near the disc's fissure using techniques andapparatuses typical of percutaneous interventions. For convenience andto indicate that the apparatus of the invention can be used with anyinsertional apparatus that provides proximity to the disc, includingmany such insertional apparatuses known in the art, the term“introducer” is used to describe this aid to the method. An introducerhas an internal introducer lumen with a distal opening at a terminus ofthe introducer to allow insertion (and manipulation) of the operationalparts of the apparatus into (and in) the interior of a disc.

The operational part of the apparatus comprises an elongated elementreferred to as a catheter, various parts of which are located byreference to a distal end and a proximal end at opposite ends of itslongitudinal axis. The proximal end is the end closest to the externalenvironment surrounding the body being operated upon (which may still beinside the body in some embodiments if the catheter is attached to ahandle insertable into the introducer). The distal end of the catheteris intended to be located inside the disc under conditions of use. Thecatheter is not necessarily a traditional medical catheter (i.e., anelongate hollow tube for admission or removal of fluids from an internalbody cavity) but is a defined term for the purposes of thisspecification. “Catheter” has been selected as the operant word todescribe this part of the apparatus, as the inventive apparatus is along, flexible tube which transmits energy and/or material from alocation external to the body to a location internal to the disc beingaccessed upon, such as a collagen solution and heat to the annularfissure. Alternatively, material can be transported in the otherdirection to remove material from the disc, such as removing material byaspiration to decrease pressure which is keeping the fissure open andaggravating the symptoms due to the fissure.

The catheter is adapted to slidably advance through the introducerlumen, the catheter having an probe section at the distal end of thecatheter, the probe section being extendible through the distal openingat the terminus of the introducer into the disc. Although the length ofthe probe portion can vary with the intended function as explained indetail below, a typical distance of extension is at least one-half thediameter of the nucleus pulposus, preferably in the range of one-half toone and one-half times the circumference of the nucleus.

In order that the functional elements of the catheter (e.g., anelectromagnetic probe, such as, an RF electrode or a resistance heater)can be readily guided to the desired location within a disc, the probeportion of the catheter is manufactured with sufficient rigidity toavoid collapsing upon itself while being advanced through the nucleuspulposus and navigated around the inner wall of the annulus fibrosus.The probe portion, however, has insufficient rigidity to puncture theannulus fibrosus under the same force used to advance the catheterthrough the nucleus pulposus and around the inner wall of the annulusfibrosus. Absolute penetration ability will vary with sharpness andstiffness of the tip of the catheter, but in all cases a catheter of thepresent invention will advance more readily through the nucleus pulposusthan through the annulus fibrosus.

In preferred embodiments, the probe section of the catheter further hasdifferential bending ability in two orthogonal directions at rightangles to the longitudinal axis. This causes the catheter to bend alonga desired plane (instead of at random). Also when a torsional (twisting)force is applied to the proximal end of the catheter to re-orient thedistal end of the catheter, controlled advancement of the catheter inthe desired plane is possible.

A further component of the catheter is a functional element located inthe probe section for diagnosis or for adding energy and adding and/orremoving material at the selected location of the disc where the annulartear is to be treated. The apparatus allows the functional element to becontrollably guided by manipulation of the proximal end of the catheterinto a selected location for localized treatment of the annular fissure.

The method of the invention, which involves manipulating disc tissue atthe annular fissure, is easily carried out with an apparatus of theinvention. An introducer is provided that is located in a patient's bodyso that its proximal end is external to the body and the distal openingof its lumen is internal to the body and (1) internal to the annulusfibrosus or (2) adjacent to an annular opening leading to the nucleuspulposus, such as an annular tear or trocar puncture that communicateswith the nucleus pulposus. Te catheter is then slid into position in andthrough the introducer lumen so that the functional element in thecatheter is positioned at the selected location of the disc by advancingor retracting the catheter in the introducer lumen and optionallytwisting the proximal end of the catheter to precisely navigate thecatheter. By careful selection of the rigidity of the catheter and bymaking it sufficiently blunt to not penetrate the annulus fibrosus, andby careful selection of the flexibility in one plane versus theorthogonal plane, the distal portion of the catheter will curve alongthe inner wall of the annulus fibrosus as it is navigated and isselectively guided to an annular tear at selected location(s) in thedisc. Energy is applied and/or material is added or removed at theselected location of the disc via the functional element.

Each of the elements of the apparatus and method will now be describedin more detail. However, a brief description of disc anatomy is providedfirst, as sizes and orientation of structural elements of the apparatusand operations of the method can be better understood in some cases byreference to disc anatomy.

An Exemplary Surgical Site

The annulus fibrosus is comprised primarily of tough fibrous material,while the nucleus pulposus is comprised primarily of an amorphouscolloidal gel. There is a transition zone between the annulus fibrosusand the nucleus pulposus made of both fibrous-like material andamorphous colloidal gel. The border between the annulus fibrosus and thenucleus pulposus becomes more difficult to distinguish as a patientages, due to degenerative changes. This process may begin as early a 30years of age. For purposes of this specification, the inner wall of theannulus fibrosus can include the young wall comprised primarily offibrous material as well as the transition zone which includes bothfibrous material and amorphous colloidal gels (hereafter collectivelyreferred to as the “inner wall of the annulus fibrosus”). Functionally,that location at which there is an increase in resistance to catheterpenetration and which is sufficient to cause bending of the distalportion of the catheter into a radius less than that of the internalwall of the annulus fibrosus is considered to be the “inner wall of theannulus fibrosus.”

As with any medical instrument and method, not all patients can betreated, especially when their disease or injury is too severe. There isa medical gradation of degenerative disc discase (stages 1-5). See, forexample, Adams et al., “The Stages of Disc Degeneration as Revealed byDiscograms,” J. Bone and Joint Surgery, 68, 3641 (1986). As these gradesare commonly understood, the methods of instrument navigation describedherein would probably not be able to distinguish between the nucleus andthe annulus in degenerative disease of grade 5. In any case, mosttreatment is expected to be performed in discs in stages 3 and 4, asstages 1 and 2 are asymptomatic in most patients, and stage 5 mayrequire disc removal and fusion.

Some of the following discussion refers to motion of the catheter insidethe disc by use of the terms “disc plane,” “oblique plane” and“cephalo-caudal plane.” These specific terms refer to orientations ofthe catheter within the intervertebral disc.

Referring now to the figures, FIGS. 2A and 2B illustrate one embodimentof a catheter 200 of the invention as it would appear inserted into thelumen 214 of an introducer 210. The apparatus shown is not to scale, asan exemplary apparatus (as will be clear from the device dimensionsbelow) would be relatively longer and thinner; the proportions used inFIG. 2A were selected for easier viewing by the reader. The catheter 200includes handle 206, stem 208, probe section 216 and a tip 220. Thehandle 206 at the proximal end of the catheter is coupled via the stem208 to the probe section 216, which is located proximate the distal endof the device. At the terminus of the probe, i.e., the distal end of thedevice, is the tip 220. The tip may be axially displaced from the probesection. Functional elements 222 for delivery or energy or material toor from the site may be placed within the probe. These may, viaconnections within the probe, stem and handle, be coupled to either anenergy delivery device 202 or a material transfer device 204. Thereforeno limitation should be placed on the types of energy, force, ormaterial transporting elements present in the catheter. These are merelysome of the possible alternative functional elements that can beincluded in the probe portion of the catheter. The flexible, movablecatheter 200 is at least partially positionable in the introducer lumen214, to bring the probe section, which is designed to be the portion ofthe catheter that will be pushed out of the introducer lumen and intothe nucleus pulposus and into the selected location(s) with regard tothe annular tear. Dashed lines are used to illustrate bending of theprobe portion of the catheter as it might appear under use, as discussedin detail later in the specification.

FIG. 2B shows an axial cross-section of stem 208 at the proximal end ofthe catheter. In this embodiment of the invention the stem has an ovalshape, as does the lumen 214 thus allowing the rotational orientation ofthe probe to be fixed with respect to the introducer. Other sections andproperties of catheter 200 are described later.

For one embodiment suitable for intervertebral discs, the outer diameterof catheter 200 is in the range of 0.2 to 5 mm, the total length ofcatheter 200 (including the portion inside the introducer) is in therange of 10 to 60 cm, and the length of introducer 210 is the range of 5to 50 cm. For one preferred embodiment, the catheter has a diameter of 1mm, an overall length of 30 cm, and an introduced length of 15 cm (forthe probe section). With an instrument of this size, a physician caninsert the catheter for a distance sufficient to reach selectedlocation(s) in the nucleus of a human intervertebral disc.

Any device in which bending of the tip of a catheter of the invention isat least partially controlled by the physician is “actively steerable.”A mandrel may facilitate the active steering of a catheter.

Active Steering of Catheter

Referring now to FIG. 2B, a guiding mandrel 232 can be included both toadd rigidity to the catheter and to inhibit movement of probe section216 of the catheter 200 along an inferior axis 242 while allowing italong a superior axis 240 while positioned and aligned in the disc planeof a nucleus pulposus 120. This aids the functions of preventingundesired contact with a vertebra and facilitating navigation. Themandrel can be flattened to encourage bending in a plane (the “plane ofthe bend”) orthogonal to the “flat” side of the mandrel. “Flat” here isa relative term, as the mandrel can have a D-shaped cross-section, oreven an oval or other cross-sectional shape without a planar face on anypart of the structure. Regardless of the exact configuration, bendingwill preferentially occur in the plane formed by the principallongitudinal axis of the mandrel and a line connecting the oppositesides of the shortest cross-sectional dimension of the mandrel (the“thin” dimension). To provide sufficient resistance to the catheterbending out of the desired plane while encouraging bending in thedesired plane, the minimum ratio is 1.25:1 (“thickest” to “thinnest”cross-sectional dimensions along at least a portion of the probesection). The maximum ratio is 20:1, with the preferred ratio beingbetween 1.5:1 and 16:3, more preferably between 2:1 and 3.5:1. Theseratios are for a solid mandrel and apply to any material, as deflectionunder stress for uniform solids is inversely proportional to thethickness of the solid in the direction (dimension) in which bending istaking place. For other types of mandrels (e.g., hollow or non-uniformmaterials), selection of dimensions and/or materials that provide thesame relative bending motions under stress are preferred.

A catheter of the present invention is designed with sufficienttorsional strength (resistance to twisting) to prevent undesireddirectional movement of the catheter. Mandrels formed from materialshaving tensile strengths in the range set forth in the examples of thisspecification provide a portion of the desired torsional strength. Othermaterials can be substituted so long as they provide the operationalfunctions described in the examples and desired operating parameters.

While the mandrel can provide a significant portion of the columnstrength, selective flexibility, and torsional strength of a catheter,other structural elements of the catheter also contribute to thesecharacteristics. Accordingly, it must be kept in mind that it is thecharacteristics of the overall catheter that determine suitability of aparticular catheter for use in the methods of the invention. Similarly,components inside the catheter, such as a heating element or pottingcompound, can be used to strengthen the catheter or provide directionalflexibility at the locations of these elements along the catheter.

It is not necessary that the guiding mandrel 232 be flattened along itsentire length. Different mandrels can be designed for different sizeddiscs, both because of variations in disc sizes from individual toindividual and because of variations in size from disc to disc in onepatient. The bendable portion of the mandrel is preferably sufficient toallow probe section 216 of the catheter to navigate at least partiallyaround the inner wall of the annulus fibrosus (so that the operationalfunctions of the catheter can be carried out at desired location(s)along the inner wall of the annulus fibrosus). Shorter bendable sectionsare acceptable for specialized instruments. In most cases, a flatteneddistal portion of the mandrel of at least 10 mm, preferably 25 mm, issatisfactory. The flattened portion can extend as much as the entirelength of the mandrel, with some embodiments being flattened for lessthan 15 cm, in other cases for less than 10 cm, of the distal end of theguide mandrel.

In preferred embodiments, the guide mandrel or other differentialbending control element is maintained in a readily determinableorientation by a control element located at the proximal end of thecatheter. The orientation of the direction of bending and its amount canbe readily observed and controlled by the physician. One possiblecontrol element is simply a portion of the mandrel that extends out ofthe proximal end of the introducer and can be grasped by the physician,with a shape being provided that enables the physician to determine theorientation of the distal portion by orientation of the portion in thehand. For example, a flattened shape can be provided that mimics theshape at the distal end (optionally made larger to allow better controlelements capable of grasping the proximal end of the mandrel or otherbending control element can be used if desired, including but notlimited to electronic, mechanical, and hydraulic controls for actuationby the physician.

The guide mandrel can also provide the function of diffferentialflexibility by varying the thickness in one or more dimensions (forexample, the “thin” dimension, the “thick” dimension, or both) along thelength of the mandrel. A guide mandrel that tapers (becomes graduallythinner) toward the distal tip of the mandrel will be more flexible andeasier to bend at the tip than it is at other locations along themandrel. A guide mandrel that has a thicker or more rounded tip thanmore proximal portions of the mandrel will resist bending at the tip butaid bending at more proximal locations. Thickening (or thinning) canalso occur in other locations along the mandrel. Control of thedirection of bending can be accomplished by making the mandrel moreround, i.e., closer to having 1:1 diameter ratios; flatter in differentsections of the mandrel; or by varying the absolute dimensions(increasing or decreasing the diameter). Such control over flexibilityallows instruments to be designed that minimize bending in some desiredlocations (such as the location of connector of an electrical element toavoid disruption of the connection) while encouraging bending in otherlocations (e.g., between sensitive functional elements). In this manner,a catheter that is uniformly flexible along its entire length, isvariably flexible along its entire length, or has alternating moreflexible and less flexible segment(s), is readily obtained simply bymanufacturing the guide mandrel with appropriate thickness at differentdistances and in different orientations along the length of the mandrel.Such a catheter will have two or more different radii of curvature indifferent segments of the catheter under the same bending force.

In some preferred embodiments, the most distal 3 to 40 mm of a guidemandrel is thinner relative to central portions of the probe section toprovide greater flexibility, with the proximal 10 to 40 mm of the probesection being thicker and less flexible to add column strength andfacilitate navigation.

The actual dimensions of the guide mandrel will vary with the stiffnessand tensile strength of the material used to form the mandrel. In mostcases the mandrel will be formed from a metal (elemental or an alloy) orplastic that will be selected so that the resulting catheter will havecharacteristics of stiffness and bending that fall within the statedlimits. Additional examples of ways to vary the stiffness and tensilestrength include transverse breaks in a material, advance of thematerial so that it “doubles up,”-additional layers of the same ordifferent material, tensioning or relaxing tension on the catheter, andapplying electricity to a memory metal.

Multi-Dimensional Probe Deployment

Catheters which are actively steerable, may include additionally thecapability of deploying into planar substantially two dimensional shapesor three dimensional shapes which conform to the surgical site. Thesemulti-dimensional deployment capabilities, reduce operating time,improve operational accuracy and increase the utility of surgicalintervention.

Linear to Arcuate Transition of Probe

The following FIGS. 3-9 show apparatus and methods for transition aprobe from a linear to a multi-dimensional shape. The transition of theprobe from a linear to an arcuate shape may be brought about by any of agroup of activation elements including, but not limited to, thefollowing.

In an embodiment of the invention the probe may include a resilientmaterial, e.g. a heat treated metal or spring metal, which will assume alinear shape only by virtue of the guiding force of the lumen portion ofthe introducer and will resume its original arcuate shape, uponintroduction to the surgical site and by extension beyond the confinesof the introducer. The resilient spring-like material is arcuate in theabsence of external stress but, under selected stress conditions (forexample, while the catheter is inside the introducer), is linear. Such abiased distal portion can be manufactured from either spring metal orsuperelastic memory material (such as Tinel.RTM. nickel-titanium alloy,Raychem Corp., Menlo Park Calif.). The introducer (at least in the caseof a spring-like material for forming the catheter) is sufficientlystrong to resist the bending action of the bent tip and maintain thebiased distal portion in alignment as it passes through the introducer.Compared to unbiased catheters, a catheter with a biased probeencourages advancement of the probe substantially in the direction ofthe bend relative to other lateral directions. Biasing the catheter tipalso further decreases likelihood that the tip will be forced throughthe annulus fibrosus under the pressure used to advance the catheter. Inthose embodiments utilizing a resilient material an introducer incombination with the resilient material is necessary in order tointroduce the probe in a linear or lay flat configuration to thesurgical site.

Although an introducer may also be used with any of the followingactivation elements it is not necessary to bring about the transitionfrom a linear to an arcuate shape.

In another embodiment of the invention the probe may at least twomaterials with a different coefficient of thermal expansion joined toone another along their length, such that at one temperature, e.g., roomtemperature they are linear while at an elevated temperature, thedifferential expansion of one with respect to the other induces anarcuate bending of both. Bi-metallic strips such as copper and steelmight serve this function. Any other two metals with differentcoefficients of expansion could be substituted for copper and steel. Thegreater the differential of the coefficients of expansion between thetwo metals the smaller the radius(s) of the arcuate shape formed therebyat any given temperature differential. Other materials besides metalswith different coefficients of expansion could also be used. Thetemperature differential of the at least two materials at roomtemperature and at the surgical site may be increased by energydelivered to the probe, e.g. RF or resistive heating. Alternately,electrical power may be directly applied directly to one or both of theat least two materials provided they are electrically resistive suchthat the application of power will result in heat generation.

In another embodiment of the invention the arcuate shape may be broughtabout by use of materials with temperature dependent shape memory suchas the metal alloy Nitinol. The probe is fabricated to be linear at roomtemperature and arcuate at the temperature of the surgical site may beincreased by energy delivered to the probe, e.g. RF or resistiveheating. Alternately the electrical power may be directly applieddirectly to the Nitenol which is itself a resistive element.

In another embodiment of the invention the arcuate shape may be inducedelectrical activated expansion and contraction of materials within theprobe. Piezoelectric crystals positioned on either the exterior orinterior radius of the arc may be used in this manner to respectivelyexpand or contract against a surface of a mandrel within the probe, toinduce an arcuate shape.

In still another embodiment of the invention the alteration of shapefrom linear to arcuate may be produced by mechanical means such as thecombination of a draw wire and mandrel, coupled at the tip of the deviceand extending the length of the catheter, such that tension of the drawwire induces tension on a side of the mandrel inducing it to assume anarcuate shape. Numerous combinations of material and energy, eitherthermal or electrical can be used to create a deformable tip.

An advantageous feature of all the probes set forth in the currentinvention is that their shape can be configured to conform to theinterior shape of the surgical site to which they are introduced, thusplacing functional elements on the probe into proximity with allportions of the surgical site without the need for a point-by-pointnavigation of the probe tip about the surgical site.

FIG. 3 shows an embodiment of a surgical catheter with a shape shiftingprobe portion. The catheter 300 includes handle 306, stem 308 probesection 316 and tip 320. The handle 306 at the proximal end of thecatheter is coupled via the stem 308 to the probe section 316, which islocated proximate the distal end of the device. At the terminus of theprobe, i.e. the distal end of the device, is the tip 320. In theembodiment show the probe is fabricated from a resilient material thusrequiring an introducer to effect its transition from a linear to anarcuate shape. In alternate embodiments any of the other activationelements described above could be utilized to effect a transition of theprobe section from a linear to a multi-dimensional shape.

FIGS. 4A-D show the sequence of operations associated with the insertionof the probe section 316 of the catheter 300 shown in FIG. 3 into thenucleus pulposus 120 of a spinal disc. In FIG. 4A the terminus of lumen214 (See FIG. 2A) has been introduced into the nucleus pulposus of thedisc substantially tangent to the interior sidewall of the disc.

In FIG. 4B handle and stem, respectively, 306-308 of the catheter areinserted further into the introducer 210 so that the tip 320 of theprobe section begins to extrude into the intradiscal space.

In FIGS. 4C-D the insertion continues until the probe section 316 hasformed a complete circle, with the tip 320 adjacent to the lumen 214 ofthe introducer 210. In the embodiment shown, the plane defined by thearcuate probe is coplanar with the intradiscal plane defined by theintervertebral disc. Once the probe has deployed within the intradiscalcavity it may be further position by movement either of the introduceror the catheter. When the probe is properly deployed, functionalelements on the probe may be used to introduce heating or cooling of theintradiscal cavity or of selected portions thereof (See FIGS. 10A-B,11). In alternate embodiments of the invention the functional elementmay include a lumen for the introduction and/or removal of material intothe surgical site. (See FIGS. 12A-C). In still other embodiments in theinvention the probe tip may include a surgical knife, either alone or incombination with a lumen. (See FIGS. 12A-C). In still other embodimentsin the invention the probe tip may include a surgical knife, eitheralone or in combination with a lumen. (See FIGS. 12A-C).

To trace the location of a catheter probe within a surgical site variousimaging techniques may be used. A radiographically opaque marking devicecan be included in the distal portion of the catheter (such as in thetip or at spaced locations throughout the probe Portion) so thatadvancement and positioning of the probe section can be directlyobserved by radiographic imaging. Such radiographically opaque markingcan be any of the known (or newly discovered) materials or devices withsignificantly opacity. Examples include but are not limited to a steelmandrel sufficiently thick to be visible on fluoroscopy, atantalum/polyurethane tip, a gold-plated tip, bands of platinum,stainless steel or gold, soldered spots of gold and polymeric materialswith radiographically opaque filler such as barium sulfate. A resistiveheating element or an RF electrode(s) may provide sufficientradio-opacity in some embodiments to serve as a marking device.

FIG. 5 shows an alternate embodiment of the catheter with an inwardspiraling probe portion. The catheter 500 has a handle 306 coupled viastem 308 to the spiral probe section 516. The spiral probe sectionterminates at the distal end of the catheter in a tip 520.

As described and discussed above, the catheter may be caused to attain aspiral shape by numerous activation elements including the use ofmaterials which are: resilient or bimetallic, which exhibit temperaturedependent shape memory, by materials in which electrical expansion andcontraction may be induced, and by mechanical means. A possibleadvantage of the inward spiraling shape is that material may be sweptduring deployment of the probe radially inward/outward.

FIG. 6A-B show respectively elevation and side views of an alternateembodiment of a catheter with a catheter 600 with an outward spiralingprobe. Probe section 616 is coupled via stem 308 to handle 306. Tip 620is at the terminus of the Probe 616 at the distal end of the catheter600. As is evident in FIG. 6B the stem 308 intersects at an acute anglethe plane defined by the spiral probe section 616. Such alteration ofthe plane of the probe with respect to the stem may result in improvedconformity of the probe with the intradiscal cavity or other joint intowhich the probe may be introduced.

As described and discussed above, the catheter may be caused to attain aspiral shape by numerous activation elements including the use ofmaterials which are: resilient or bi-metallic, which exhibit temperaturedependent shape memory, by materials in which electrical expansion andcontraction may be induced, and by mechanical means. A possibleadvantage of the outward spiraling shape is that material may be sweptduring deployment of the probe radially inward/outward.

the catheter 700 shown in FIG. 7-8 may be fabricated to deploy intoeither a planar two dimensional shape or into a three dimensional“eggbeater” shape which conforms to the surgical site. The catheterincludes a handle 706, a stem 708, a probe 702 and an introducer 210.The handle 706 includes a push/pull member 704. The stem 708 includes adraw member 730. The introducer 210 includes an internal lumen 214. Theprobe 702 includes side members 716 and a core member 732.

one or more of the side members 716 are arranged radially about coremember 732. The core extends axially and is attached at a distal end ofthe probe 702 to the distal ends of the side members by tip 720. At aproximal end the core joins with the draw member 730 as an axialextension thereof. The proximal ends of the side members 716 areslidably affixed to the draw member. Axially induced movement of theproximal ends of the side members along that draw member and toward thecore member 732 results in an arcuate deflection of the side membersfrom a collapsed position adjacent to the axial core to an expandedposition radially displaced about the axial core. The draw member 730extends axially the full length of the stem 708 and of the handle 706 toa point of attachment at the push/pull member 704 of the handle. Thedraw member is slidable axially within the stem. The push/pull member704 of the handle 706 is slidable axially with respect to the handle706.

In operation the side members 716 are brought into a lay-flat conditionagainst the axial core prior to introduction into the introducer. Thissituation is brought about by the positioning of push-pull memberadjacent to the handle 706. This causes the maximal extension of thedraw member from a distal end of the stem 708. In an embodiment of theinvention the lay-flat members are tension springs, which in the relaxedposition lay flat against the axial core. In this linear configuration,the tip 720 of the probe is placed into the introducer 210. When theprobe 702 is extended beyond the introducer and into the surgical site,the draw member is gradually retracted into the handle by a displacementof the push-pull member 704 away from the base portion of the handle706. This causes the distal end of the stem 708 to press the distal endsof the side members 716, thereby reducing the axial distance betweenthose members and the tip 720. As the distance is reduced, those membersassume an arcuate shape radially displaced about the axial core.

In an alternate embodiment of the invention, the side members in arelaxed position assume an arcuate shape radially displaced about theaxial core. By coupling the distal end of step 708 to the distal ends ofthe side member, an extension of the draw member resulting from movementof the push-pull member 704 toward the base portion of the handle 706causes the side members to lay flat against the axial core.

As described and discussed above, the catheter may be caused to attainthe “eggbeater” or other shapes by numerous activation elementsincluding the use of materials which are: resilient or bimetallic, whichexhibit temperature dependent shape memory, by materials in whichelectrical expansion and contraction may be induced, and by mechanicalmeans.

An Electrophoretic Functional Element

The functional element of the probes shown in FIGS. 8A-F perform anelectrophoretic function with surgically beneficial results.Electrophoresis can be defined as the movement of charged particles orsubstances through a medium in which they are dispersed as a result ofchanges in electrical potential. For example, electrophoretic methodsare useful in separating various molecular particles depending upon thesize and shape of the particle, the charge carried, the applied currentand the resistance of the medium. In addition, with the appropriateconstruction of the anode (positive) and the cathode (negative)electrodes, the chemical milieu of a surgical site, e.g. the nucleuspulposus, can be altered by electrophoretic methods, with beneficialtherapeutic effects such as pain reduction or intradiscal repair.

In clinical setting, negatively charged ions or free radicals may befound in high concentrations in chronically inflamed states of surgicalsites such as the intradiscal cavity of the spine. Disco-genic pain mayfor example be associated with higher than normal concentrations ofenzymes such as phospholipase A-2 in the spinal disc wall, or thenucleus pulposus for example. Alternately, a recently discovered shortprotein binds to cell membranes in the brain and spinal cord and may beaffected and controlled by electrophoretic methods. The peptide,nocistatin, seemed to block pain or the transmission of pain to thenociceptors or pain receptors when injected into animals. Nocistatinappears to interact with the peptide nociceptin in a manner which mayeither amplify or reduce pain depending on the relative concentrationsof the two peptides. Control of the these two peptides byelectrophoresis may prove beneficial in the treatment of back pain.

By inserting a probe into the site with a functional element capable ofperforming an electrophoretic function, it may be possible to reduce theconcentrations of the charged particles: e.g. enzymes,neurotransmitters, proteins, individual molecules, or free radicals toachieve one or more beneficial therapeutic effects including but notlimited to pain reduction, intradiscal reshaping or repair.

The concentrations may be reduced by migration of the charged particlesfrom perimeter regions of the surgical site toward the core of the site,by means of an appropriately configured probe, with electrodespositioned at the perimeter and core of the surgical site, whichelectrodes are charged in a manner designed to encourage whichever of aradially outward or inward migration of the charged particles istherapeutically beneficial.

In an embodiment of the invention, further beneficial effects may beachieved when the charge on the probe is maintained as it is withdrawnfrom the surgical site, thus encouraging the removal of the chargedparticles from the site.

FIGS. 8A-F show multi-dimensional probes with side and core membersdeployed into a multi-dimensional configuration at the surgical site.The side and core members may perform an electrophoretic function bymeans of electrical stimulus of opposite polarity applied to each. Theelectrical stimulus may be pure DC or rectified AC at frequenciesincluding the radio frequency range.

In FIG. 8A, side members 816 naturally assume an arcuate configurationradially displaced about core 832. They may be compressed against thecore as is the case when they are within the lumen 214 within theintroducer 210. As they collectively extended through the lumen and intothe surgical site their internal spring tension causes them to assume anarcuate configuration radially displaced about the core. At thecompletion of the surgery they may be withdrawn into the lumen, and inso doing, collapse against the core.

In an embodiment of the invention central core 832 provides structuralsupport to the tip of the probe. Additionally, central core 832 issurrounded by membrane 833 which serves as a central collector regionfor the electrophoresis. In another embodiment of the invention themembrane 833 may itself serve as an electrode.

As described and discussed above, the catheter may be caused to attainthe “eggbeater” or other shapes by numerous activation elementsincluding the use of materials which are: resilient or bimetallic, whichexhibit temperature dependent shape memory, by materials in whichelectrical expansion and contraction may be induced, and by mechanicalmeans.

Via electrical connections, the side members 816 and core 832 mayperform as electrodes. In an embodiment of the invention the sidemembers and core member are coupled to electrical power to serve asrespectively either anodes-cathode or cathodes-anode to one another. Theelectrical connections couple the electrodes to a source of power whichmay be located in the catheter or be externally coupled to theelectrodes through a coupling on the handle of the catheter. (See FIGS.13-14). This arrangement may have certain surgical benefits.

By allowing the side members and core to serve as respectively perimeterand core electodes the core can be charged providing an electricalgradient for electrophoresis to pull charged particles from a perimeterregion in the disc to the core. The charge of the core 832 electrode maybe continuously maintained during collapse of the side members andretraction of the probe from the surgical site, to remove the chargedparticles from the surgical site, e.g. the nucleus pulposus. This wouldeffect a change to the nucleus pulposus and reduce the electricalpotential on the nociceptors, i.e. pain receptors, thereby reducing painperception as well as removing material from the disc.

In another embodiment of the invention, electrically charged particlesmay be introduced into the intradiscal cavity by means of membrane 833.Upon deployment of the side members at the surgical site, andappropriate charging of the side and perimeter members the chargedparticles may be encouraged to migrate toward the side members therebyaffecting a change of the chemical milieu of the site.

FIGS. 8B-D shows demonstratively alternate functional embodiments of theprobe 820 deployed in relation to the intradiscal cavity which containsthe nucleus pulposus 120.

FIG. 8B shows one functional embodiment of the invention where sidestructural members serve as a cathode 826 while central core serves asan anode 842. Under application of direct current, the negativelycharged particles are drawn toward anode 842.

FIG. 8C shows probe 820 where side structural members serve as anode 842while the core serves as cathode 826.

FIG. 8D shows another embodiment where the core 832 is not an electrodeand side structural members serve as individual electrodes. Sidestructural members are each charged differently with one structuralmember serving as anode 842 and the other side structural member servingas cathode 826.

FIG. 8E shows an alternative embodiment of the functional aspect ofprobe 820 with additional intermediate side members 835. Intermediateside members 835 are, in a deployed state located radially between thecore and an associated one of the side members. Intermediate sidemembers 835 are each electrically coupled to a corresponding one of sidemembers 816 by means of electrical connectors/ribs 825. The ribs createa greater electrical potential by increasing the electrode region. Theindividual ribs 825 may be constructed of the same material asintermediate side members 835 or any other electrically conductivematerial. The “fishrib” or fan-shaped structure of probe 820 in thisembodiment creates a greater driving force for changing the chemicalmilieu of the intradiscal cavity by electrophoretic means.

FIG. 8F is an embodiment whereby the greater electrical potential iscreated by increasing the surface area of the electrode region by use ofa film 822 with an electrically conductive layer, e.g. vacuum metalizedpolyester. The conductive layer may be continuous or patterned. Opposingsides of the film are affixed to respective ones of intermediate sidemembers 837 and side members 816. As the tip is deployed and expands toform an arcuate shape the film is deployed to expose the electricallyconductive layer. The electrical gradient created is similar to FIG. 8Ewhere a greater driving force pushes the negatively charged particlestowards the central anode.

In another embodiment of the invention, the electrophoretic probe may beimplemented utilizing a probe which, unlike the probes disclosed above,is substantially linear in shape. In this embodiment, electrophoreticfunctionality is achieved by axially displaced electrodes on the probewhich are energized to opposing polarity to effect a migration ofcharged particles from one electrode to the other, to achieve abeneficial therapeutic effect.

FIGS. 9A-D show the insertion stages of the catheter at a surgicaljoint, in this case the intevertebral disc and specifically the nucleuspulposus 120 thereof. The device being inserted is the catheter 700shown in FIG. 7.

FIG. 9A shows the introducer 210 positioned so that the lumen at itsdistal end is within the intradiscal cavity. The stem 708 connects thehandle 706 to the probe 702. The push-pull member 704 of the handle 706is in the inserted position proximate to the handle.

In that position the draw member 730 (not shown) is fully extended andthe collapsible side members 716 lay flat against the axial core member732 within the intradiscal cavity.

FIGS. 9B-D show various stages of the expansion of collapsible sidemembers 716 radially about axial core member 732. This deployment isbrought about by the retraction of the draw member 730 (not shown)through stem 708 by means of the displacement of the push-pull member704 away from the handle 706.

Functional Elements

Since a purpose of the inventive catheter is to repair tears or fissuresin a disc by operation of the instrument at the tear location adjacentto or inside the disc, a functional element is provided in or on thecatheter to carry out that purpose.

Non-limiting examples of functional elements include any element capableof aiding diagnosis, delivering energy, or delivering or removing amaterial from a location adjacent the element's location in thecatheter, such as an opening in the catheter for delivery of a fluid(e.g., dissolved collagen to seal the fissure) or for suction, a thermalenergy delivery device (heat source), a mechanical grasping tool forremoving or depositing a solid, a cutting tool (which includes allsimilar operations, such as puncturing), a sensor for measurement of afunction (such as electrical resistance, temperature, or mechanicalstrength), or a functional element having a combination of thesefunctions.

The functional element can be at varied locations in the probe portionof the catheter depending on its intended use. Multiple functionalelements can be present, such as multiple functional elements ofdifferent types (e.g., a heat source and a temperature sensor) ormultiple functional elements of the same type (e.g., multiple heatsources spaced along the probe portion).

One of the possible functional elements present on probe section 216 isa thermal energy delivery device. A variety of different types ofthermal energy can be delivered including but not limited to resistiveheat, radio frequency (RF), coherent and incoherent light, microwave,ultrasound and liquid thermal jet energies. In one embodiment, thermalenergy delivery device is positioned proximal to the distal portion ofprobe section 216 so that there is no substantial delivery of energy atthe distal portion, which can then perform other functions without beingconstrained by being required to provide energy (or resist the resultingheat).

The energy directing device is configured to limit thermal and/orelectromagnetic energy delivery to a selected site of the disc and toleave other sections of the disc substantially unaffected. The energycan be directed to the walls of the fissure to cauterize granulationtissue and to shrink the collagen component of the annulus, while thenucleus is shielded from excess heat.

In various embodiments, catheter probe section 216 and/or tip 220 arepositionable to selected site(s) around and/or adjacent to inner wall ofan annulus fibrosus for the delivery of therapeutic and/or diagnosticagents including but not limited to, electromagnetic energy,electrolytic soloutions, contrast media, pharmaceutical agents,disinfectants, collagens, cements, chemonucleolytic agents and thermalenergy. Probe section 216 is navigational and can reach the posterior,the posterior lateral, the posterior medial, anterior lateral, andanterior medial regions of the annulus fibrosus, as well as selectedsection(s) on or adjacent to inner wall of the nucleus pulposus 120.

In FIGS. 10A-B, 11, and 12A-C, embodiments of the catheter are shown inwhich the probe delivers thermal energy to reduce pain without ablationor removal of any disc material adjacent to and with or without removalof water vapor from the disc but without charring the nucleus. The probesection also can heat the collagen components of the annulus, therebyshrinking the annulus, with or without desiccating local tissue.

FIGS. 10A-B show alternate embodiments of a probe and tip, which includea functional elements with the capability of delivering energy to thesurgical site. In FIG. 10A, the functional elements exhibit combinedresistive and radio frequency energy delivery capability. In FIG. 10B,the device includes dual resistive heating capability.

FIG. 10A, the distal portion of a probe 1000 is shown. The probe istubular with an interior wall 1006. At the distal end of the probe a tip1002 is affixed to the probe. Within the interior of the probe aresistive heating coil 1012 is positioned. The resistive heating coil iscoupled via wires 1014 extending through the stem and handle to anenergy delivery device 202 (see FIG. 2A). In the embodiment shown, theprobe itself is electrically conductive, thus allowing for the deliveryof R.F. power to tip 1002 at the terminus of the probe 1000. The tip incombination with a return pad (not shown) affixed to the patient,provides monopolar R.F. delivery to the surgical site. To prevent R.F.power emanating from the exterior of the probe, an outer sheath 1004,which is electrically insulating, is provided to surround all except theterminus of probe 1000. To measure the temperature at the tip, atemperature sensing device 1018 is positioned inside the tip. Thatdevice is coupled via wires 1020 which extend the length of the stem tothe handle to external controls for monitoring energy to the surgicalsite. Heating coil 1012 may be powered by a direct current source (andless preferably a source of alternating current). Heating coil 1012 ismade of a material that acts as a resistor. Suitable materials includebut are not limited to stainless steel, nickel/chrome alloys, platinum,and the like. Preferably, the heating element is inside the probe. Theresistive material is electrically insulated and substantially nocurrent escapes into the body. With increasing levels of current, thecoils heat to greater temperature levels. In one embodiment, 2 wattspass through heating element 46 to produce a temperature of about 55.degree. C. in a selected target such as fissure, 3 watts produces 65.degree. C., 4 watts produces 75. degree. C., and so on.

FIG. 10B shows an alternate embodiment of the energy delivery element.In this embodiment dual resistive/radio-frequency heat delivery isprovided. The probe 1050 defines an interior lumen portion in which tip1052 is placed. Short and long heating elements, respectively 1062-1068,are positioned around the exterior of the probe, and are electricallyconnected using wires (not shown) to energy delivery device 202 (seeFIG. 2A). To monitor the temperature of each of the coils thermocouples1070 and 1072 are provided.

In another embodiment, radio frequency energy is delivered to theheating elements. As illustrated in FIG. 10B coils 1062, 1068 arepositioned on the exterior of probe 1050 and serve as RF electrodespowered by an RF generator. The electrodes are made of suitablematerials including but not limited to stainless steel or platinum.Increasing levels of current conducted into disc tissue heat that tissueto greater temperature levels. A circuit can be completed substantiallyentirely at probe section 16 (bipolar device) or by use of a secondelectrode attached to another portion of the patient's body (monopolardevice). In either case, a controllable delivery of RF energy isachieved.

In another embodiment sufficient energy is delivered to theintervertebral disc to heat and shrink the collagen component of theannulus but not ablate tissue adjacent to catheter 14. With a resistiveheating device, the amount of thermal energy delivered to the tissue isa function of (i) the amount of current passing through heating element,(ii) the length, shape, and/or size of the heating element, (iii) theresistive properties of the heating element, (iv) the gauge of theheating element, and (v) the use of cooling fluid to controltemperature. All of these factors can be varied individually or incombination to provide the desired level of heat. Energy delivery device202 associated with the heating element may be battery based. Thecatheters can be sterilized and may be disposable.

FIG. 11 shows an alternate embodiment for the construction of resistiveheating coils. In the embodiment shown, a thin film resistive element,generally 1100, fabricated using technology derived from printed circuitboards, is provided. In this embodiment, the resistive wire 1106 isfabricated as part of a substrate or film 1108, usingphoto-etch/engraving techniques. The substrate might for example be apolyester film. The wire may be internal to or deposited on a surface ofthe substrate. The coil can be fabricated on one side only of thesubstrate of film 1108, thus allowing for asymmetric delivery of heat.In assembly, the core can be positioned in the interior of the probe orheat shrunk around the exterior of the probe.

FIGS. 12A-C show an alternate embodiment of the invention in which anumber of functional elements are provided including a retractableblade, a lumen and a resistive heating element. FIG. 12A shows anexterior side view of probe 1200. FIG 12B shows a cross-sectional sideview of the probe 1200. FIG. 12C shows a cross-sectional axial view fromthe probe interior facing the tip end of the probe.

FIG. 12A shows the probe 1200, generally tubular in shape, with anexterior tubular portion 1202. At the distal end of the probe a tip 1204is affixed. The tip defines in its face, a lumen opening 1206 in whichthe cutting tip of a retractable blade 1208 is shown in the retractedposition. In an embodiment of the invention, the exterior dimensions ofthe retracted blade are sufficiently less than the interior dimensionsof the lumen 1206 so as to allow for not only the refraction andextension of the blade, but also for either the removal by suction orintroduction by pressure of material from or to the surgical site.

FIG. 12B shows the cross-sectional view of the probe shown in FIG. 12A.In addition to the features discussed above, the device is seen toinclude resistive heating coils 1210 contained within a spacing betweenthe exterior tubular portion 1202 and an interior tubular portion 1212of the probe 1200. The retractable blade is in turn slidably positionedwithin the interior tubular portion.

FIG. 12C shows a cross-sectional view facing toward the end of probe1200. The exterior tubular portion 1202 and the interior tubular portion1212 of the probe 1200 are shown. In the spacing between them theresistive heating coils 1210 are shown. The blade 1208 is axiallypositioned within the inner tubular wall 1212.

The lumen 1206 may be configured to transport a variety of differentmediums including but not limited to electrolytic solutions (such asnormal saline), contrast media (such as Conray meglumine iothalamate),pharmaceutical agents, disinfectants filling or binding materials suchas collagens or cements, chemonucleolytic agents and the like, from thematerial delivery/removal device 204 (see FIG. 2A) to a desired locationwithin the interior of a disc (i.e., the fissure). Further, the lumencan be used to remove nucleus material or excess liquid or gas(naturally present, present as the result of a liquefying operation, orpresent because of prior introduction) from the interior of a disc. Whenused to transport a fluid for irrigation of the location within the discwhere some action is taking place (such as ablation, which generateswaste material), the lumen is sometimes referred to as an irrigationlumen. The lumen can be coupled to the material delivery/removal device204 through the catheter. In addition to or in substitution for thecutting blade, other instruments can be delivered through the lumenincluding but not limited to: graspers, drill and biopsy needle.

FIG. 13 shows a split interface generally 1300 for providing connectionsof n the handle of the catheter to join energy delivery and materialtransfer elements within the probe 216 (See FIG. 2A) of the catheter tomaterial delivery/removal device 204 and energy delivery device 202 (seeFIG. 2A). An electrical interface 1302, a luer interface 1306 for fluidsand an auxiliary interface 1304 are shown. The auxiliary interface couldbe utilized for a needle syringe, graspers or an optical fiber forviewing a surgical site. As will be obvious to those skilled in the art,the probe may be configured for any one or all of these functionalelements.

FIG. 14 shows an integrated interface 1400 for providing connections onthe handle of the catheter to join energy delivery and material transferelements within the probe 216 (See FIG. 2A) of the catheter to materialdelivery/removal device 204 and energy delivery device 202 (see FIG.2A). Electrical interfaces generally 1402 and a luer interface 1404 forthe introduction or removal of material to the surgical site are shown.External threads 1406 are shown for coupling the interface to materialand energy delivery devices.

All publications, patent applications, and issued patents mentioned inthis application are hereby incorporated herein by reference in theirentirety to the same extent as if each individual publication,application, or patent was specifically and individually indicated to beincorporated in its entirety by reference.

All the disclosed embodiments of the invention described herein can berealized and practiced without undue experimentation. Although the bestmode of carrying out the invention contemplated by the inventors isdisclosed above, practice of the present invention is not limitedthereto. Accordingly, it will be appreciated by those skilled in the artthat the invention may be practiced otherwise than as specificallydescribed herein.

For example, the individual components need not be formed int ehdisclosed shapes, or assembled int eh disclosed configuration. Further,the individual components need not be fabricated from the disclosedmaterials, but could be fabricated from virtually any suitablematerials. Furthermore, all the disclosed elements and features of eachdisclosed embodiment can be combined with; or substituted for, thedisclosed elements and features of every other disclosed embodimentexcept where such elements or features are mutually exclusive.

It will be manifest that various additions, modifications andrearrangements of the features of the present invention may be madewithout deviating from the spirit and scope of the underlying inventiveconcept. It is intended that the scope of the invention as defined bythe appended claims and their equivalents cover all such additions,modifications, and rearrangements. The appended claims are not to beinterpreted as including means-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase“means for.” Expedient embodiments of the invention are differentiatedby the appended subclaims.

1. A device for delivering energy to an intervertebral disc comprising:a catheter including a handle at a proximal end of the catheter and aprobe at a distal end of the catheter; and at least one energy deliverydevice located at the distal end of the catheter to deliver energy toportions of the intervertebral disc. wherein the probe comprises anactivation element located at the distal end of the catheter thatpredisposes the catheter body to adopt a multi-dimensional shape withinthe intervertebral disc, the activation element comprising at least twoside members extending axially along a longitudinal axis of the probeand rigidly attached at first ends thereof to the probe the at least twoside members movable from a first position proximate to the longitudinalaxis of the probe to a second position radially displaced about thelongitudinal axis of the probe.
 2. The device of claim 1 wherein the atleast two side members comprise a resilient material which in a relaxedstate effects an arcuate shape and which upon introduction of externalstress assumes a substantially linear shape.
 3. The device of claim 2further comprising an introducer defining along a longitudinal axis alumen dimensioned to apply external stress to the resilient material. 4.The device of claim 1 wherein the at least two side members comprise atleast two materials exhibiting differential coefficients of thermalexpansion and at least two materials joined to one another wherein at afirst temperature the at least two materials assume a substantiallylinear shape and at a second temperature that, at least two materialsassume an arcuate shape.
 5. The device of claim 1 wherein the at leasttwo side members comprise: a resilient material which in a relaxed stateeffects a linear shape and which upon introduction of a compressiveforce between the first ends of the at least two side members and secondends thereof assumes a substantially arcuate shape; and a draw membercoupled to the handle for applying tile compressive force to theresilient material, to effect a transition of the at least two sidemembers from a substantially linear shape to an arcuate shape.
 6. Aprobe for delivering energy to an intervertebral disc comprising: a setof side members and a core member, the set of side members movable froma first position proximate to a longitudinal axis of the probe to asecond position radially displaced about the longitudinal axis of theprobe; and electrical couplings for applying electrical power of anopposing polarity to respectively the set of side members and the coremember.
 7. The probe of claim 6 further comprising a member surroundingthe core member.
 8. The probe of claim 7 wherein electrically chargedparticles are introduced into an intradiscal cavity of theintervertebral disc by the membrane thereby changing a chemical milieuof the intradiscal cavity.
 9. The probe of claim 6 wherein the set ofside members serve as a electrophoretic cathode electrode and the coremember serves as an electrophoretic anode electrode such that underapplication of direct current, negatively charged particles are drawntoward the core member.
 10. The probe of claim 6 wherein the set of sidemembers serve as an electrophoretic anode electrode and the core memberserves as an electrophoretic cathode electrode.
 11. A device fortreating an intervertebral disc by electrophoresis comprising: anelongated catheter defining a longitudinal axis and configured to beinserted into an intervertebral disc, the catheter comprising: afirst-polarity electrophoretic electrode; and a second-polarityelectrophoretic electrode comprising, a first conductor displacedradially, with respect to the longitudinal axis, from the first-polarityelectrophoretic electrode. a second conductor displaced radially betweenthe first conductor and the first-polarity electrophoretic electrode,and a film including an electrically conductive layer extending betweenthe first conductor and the second conductor.
 12. The device of claim 11wherein the conductive layer is patterned or continuous.
 13. The deviceof claim 11 wherein the electrically conductive layer is a vacuummetalized polyester.
 14. The device of claim 11 wherein the firstpolarity electrode extends linearly along the longitudinal axis.
 15. Thedevice of claim 11 wherein the film defines opposing sides and theopposing sides are coupled to respective ones of the first conductor andthe second conductor.
 16. A multifunctional catheter for repairing anintervertebral disc comprising: an energy delivery element located at adistal end of the catheter to deliver energy to portions of theintervertebral disc; a first probe section defining along a lengththereof a first lumen; a tip coupled to the first probe section at aterminus thereof, the tip defining a second lumen aligned with the firstlumen; and a blade positioned within the first lumen and extendable froma first position within the first probe section to a second positionextending;, through the second lumen and beyond the tip, to cut selectedportions of the intervertebral disc.
 17. The catheter of claim 16further comprising a second probe section defining along a lengththereof a third lumen and the first probe section located within thethird lumen and the energy delivery element located in an annulusdefined between the second rid first probe sections.
 18. The catheter ofclaim 16 wherein the first probe section couples with a materialdelivery source to remove material from the intervertebral disc via thefirst and second lumens.
 19. The catheter of claim 16 wherein the firstprobe section couples with a material delivery source to supply materialto the intervertebral disc via tile first and second lumens.
 20. Acatheter for delivering a plurality of functional elements to anintervertebral disc to assist in the repair of (damage to theintervertebral disc comprising: a handle located at a proximal end ofthe catheter; a probe located at a distal end of the catheter; an energydelivery element located at the distal end of the catheter to deliverenergy to portions of the intervertebral disc; a material transferelement located at the distal end of the catheter to transfer materialto and from the intervertebral disc; and at least one interface on thehandle for coupling the energy delivery element and the materialtransfer element to external devices for energy and material transfer toand from the intervertebral disc.
 21. The catheter of claim 20 whereinthe interface is split or integrated.
 22. An interface for coupling acatheter to one or more external devices comprising: a first connectioncoupled to a handle of the catheter and configured to join an energydelivery element within the catheter to an energy delivery device; and asecond connection coupled to the handle and configured to join amaterial transfer element within the catheter to a material delivery orremoval device.
 23. The interface of claim 22 further comprising a thirdconnection coupled to the handle and configured to permit passage of oneor more instruments through the catheter to a surgical site.
 24. Theinterface of claim 22 wherein the first and second connections arearranged in a split configuration with respect to the handle.
 25. Theinterface of claim 22 wherein the first and second connections areintegral with the handle.
 25. A method for treating an interverteraldisc comprising: configuring a probe in a substantially linearconfiguration, the probe comprising a set of side members and a coremember; applying a force to advance the probe through a nucleus pulposusof an intervertebral disc, which force is insufficient to puncture anannulus fibrosus of the disc; deploying the set of side members from afirst position proximate to the core member to a second positionradially displaced about the core member; and delivering electricalpower of an opposing polarity to respectively the set of side membersand the core member.
 26. The method of claim 25 wherein deliveringelectrical power of an opposing polarity to respectively the set of sidemembers and the core member permits the set of side members to serve asa electrophoretic cathode electrode and the core member to serve as anelectrophoretic anode electrode such that under application of directcurrent, negatively charged particles are drawn toward the core member.27. The method of claim 25 wherein delivering electrical power of anopposing polarity to respectively the set of side members and the coremember permits the set of side members to serve as an electrophoreticanode electrode and the core member to serve as an electrophoreticcathode electrode.